This invention relates to photography and more particularly, to novel photosensitive photographic elements, particularly novel photosensitive emulsions.
As a result of the known disadvantages of gelatin, in particular, its variable photographic properties and its fixed physical properties, for example, its diffusion characteristics, much effort has been expended in the past in order to replace gelatin with a suitable synthetic grain-growing protective colloid for photographic silver halide emulsions. Many synthetic polymeric materials have heretofore been suggested as peptizers for silver halide emulsions. However, these have generally not functioned satisfactorily and frequently have not fulfilled all of the basic requirements for a photosensitive silver halide emulsion grain-growing protective colloid, which include:
(1) absent (or constant) photographic activity; PA1 (2) ability to form an adsorption layer on microcrystals of silver halide permitting stable suspensions to be obtained; PA1 (3) ability to form adsorption layers as described in (2) above which do not prevent growth of silver halide microcrystals during physical ripening; and PA1 (4) solubility in water.
In addition, heretofore, much emphasis has been placed on the ability of the synthetic polymeric material to mix with gelatin, as this property has been critical for employment in partial substitution reactions with gelatin. Consequently, many synthetic polymers of the prior art have been materials which allow for the growth of silver halide crystals only in the presence of gelatin.
Vinyl polymers comprising carbamate appendages affixed to a polyvinyl alcohol chain have been employed as vehicles and peptizers in photographic silver halide emulsions, as disclosed in Abel et al., U.S. Pat. No. 3,597,215 and Dann et al., U.S. Pat. No. 2,882,161. The above polymers have the carbamate appendage affixed to the polymeric backbone through an oxygen atom and therefore differ from the polymers of the instant invention in which the carbamate appendage is affixed to the polymeric backbone through a nitrogen atom.
Condensation products of polyalkylene oxide and N-[(dialkylamino)alkyl]carbamates have been found useful in obtaining halftone dot images of high edge gradient when incorporated in gelatino silver halide emulsions, as shown in Hayakawa et al., U.S. Pat. No. 3,288,612. Certain copolymers having N-vinyl heterocyclic carbamate monomers, particularly N-vinyloxazolidones, have been employed as flocculating agents in the manufacture of gelatino silver halide emulsions by the fluocculation method, as disclosed in Schaller et al., U.S. Pat. No. 3,360,373. Dersh U.S. Pat. Nos. 3,006,762 and 3,060,028 disclose the stabilizing and sensitizing properties of poly-N-vinyl-2-oxazolidinone polymers when added to silver halide emulsions which contain gelatin or another colloidal carrier. Casalgrasso et al. U.S. Pat. No. 3,628,957 discloses that N-alkenyl carbamate/acrylamide copolymers result in improved covering power of developed silver, increased contrast and good sensitivity when included in silver halide emulsions containing gelatin. However, gelatin-free silver halide emulsions employing N-alkenyl carbamate polymers as the grain-growing protective colloid have heretofore been unknown to the art.